Mobile incinerator with a rotary furnace, particularly for household refuse

ABSTRACT

A mobile incinerator having a rotary furnace, particularly for household refuse, mounted on the chassis of a motor vehicle. The rotary furnace is in the form of a double-walled drum which is open at both ends. The interior wall of the drum is formed by a grating comprising a plurality of thin perforated metal plates having a plurality of flow openings therethrough. The exterior wall of the drum is spaced from the grating and forms with the grating a flow chamber for a combustible gas. The flow openings in the grating introduce the combustible gas, namely fresh air, into the combustion zone defined within the interior of the rotary drum.

United States Patent Du Chambon 1 Nov. 13, 1973 [54] MOBILE INCINERATOR WITH A ROTARY 2,274,780 3/1942 Duerr et a1. 1. 110/14 FURNACE, PARTICULARLY FOR 2,601,657 6/1952 Brandt et a1.... 110/14 X 3,306,237 2/1967 Ransom, Jr. 1 110/14 HOUSEHOLD REFUSE 3,357,382 12/1967 Matteini 1. 110/14 [75] Inventor: Michel G. Du Chambon, Versailles, 3,682,115 8/1972 Rodgers 110/19 France [73] Assignee: Cigeco Compagnie des Convoyeurs Primary Examiner xenneth Sprague SA, Zug, Switzerland Attorney-Woodhams, Blanchard and Flynn [22] Filed: Jan. 14, 1972 ABSTRACT [21] Appl' 217351 A mobile incinerator having a rotary furnace, particularly for household refuse, mounted on the chassis of a [30] Foreign Application Priority Data motor vehicle. The rotary furnace is in the form of a Jan. 18, 1971 France 1. 7101430 dhhle'wahed which is Open at ehds- The interior wall of the drum is formed by a grating com- 52 us. (:1. 110/14, 110/19 prising a Plumhty of thin Perfumed metal Phites 51 Int. Cl. F23g 5/06 a plurality flow Openings herethrough The 581 Field of Search 110/8 R, 14, 19 terior Wall of the drum is Spaced the grating and forms with the grating a flow chamber for a combusti- [56] References Cited ble gas. The flow openings in the grating introduce the combustible gas, namely fresh air, into the combustion UNITED STATES PATENTS zone defined within the interior of the rotary drum. 3,682,117 8/1972 Rousseau 2,238,161 4/1941 Drew et a1. 110/14 8 Claims, 12 Drawing Figures PATENTEIJnDv 13 I915 SHEET 8 BF 7 MOBILE INCINERATOR WITH A ROTARY FURNACE, PARTICULARLY FOR HOUSEHOLD REFUSE The present invention relates to a mobile incinerator with a rotary furnace, particularly for household refuse, of the type comprising, fixed to the chassis of a motor vehicle, a rotary furnace of generally elongated shape, means for rotatably driving the furance, means of introducing matter to be incinerated through an opening leading to one end of the furnace, an ash receptacle arranged below the furnace and capable of receiving the ash passing from the other end of the furnace, a burner arranged inside said furnace, means of feeding the burner with combustible gas, means of introducing a combustible gas into the furnace, means of postcombustion, and means of cooling, purifying and evacuating burnt gases.

The invention relates particularly to an incinerator essentially for use in the collection of door-to-door refuse, the burning being continuous.

Mobile incinerators are known in which the rotary furnace comprises an internal lining made of refractory material. These furnaces have the disadvantage of being very fragile and frequent repairing of the lining is necessitated. In effect the latter is subject to significant shocks and vibrations which, together with the thermal shocks, cause rapid deterioration of the lining.

These furnaces also have the particular feature of being excessively heavy.

Attempts have been made to overcome these disadvantages by developing mobile incinerators in which the rotary furnace is made of thin sheet metal.

However, this sheet metal is subjected to high temperatures and severe chemical action owing to the oxidising agents or acids in the refuse, and it was found that the sheet metal also rapidly became unusable.

In addition to this problem of cooling of the furnace there is also a problem created by the difficulty of obtaining total combustion of all kinds of refuse, a difficulty which is very often due to poor mixing and poor ventilation of the refuse.

The object of the present invention is to overcome these disadvantages and, for this purpose, a mobile incinerator having a rotary furnace according to the invention is characterized in that the rotary furnace is in the form of a double-walled drum made of thin sheet metal and open at both ends, the interior wall forming a grill and being provided for this purpose with flow orifices, whereas the exterior wall is sealed and forms a cover or casing, and in that the said means of introducing a combustible gas into the furnace comprises mainly means of introducing fresh air into the space between the grill and the casing.

Therefore it can be seen that, prior to penetrating the furnace by passing through the grill, the fresh air for providing the oxygen necessary for combustion produces very effective cooling of the casing, and, particularly, the grill. The calories which therefore accumulate on the walls of the furnace are drawn from the interior of the latter, which also has the advantage of substantially increasing the temperature of the refuse.

On the other hand, because a large quantity of air penetrates into the furnace by passing through the grill, consequently in a transverse direction to the displacement of the refuse, this air flows over the latter, which prevents the formation of compact blocks of refuse which, as they cannot be oxygenated and therefore burnt, would be recovered almost intact in the ash receptacle.

A mobile incinerator according to the invention therefore has the advantage of comprising a rotary furnace, the life of which is increased owing to very effective cooling of its walls, which reduces maintenance costs as well as the frequency with which the incinerator is inoperative.

The efficiency of such an incinerator is also increased because the refuse is much more vigorously mixed and exposed to air than in incinerators where only the rotary movement of the furnace can ensure this mixing, and this makes it possible to improve the use of the calories provided by the combustible, and therefore to the consumption of the latter;

A mobile incinerator according to the invention can also be characterized in that the means of introducing a combustible gas into the furnace further comprises a ventilator for evacuating combustion gases leading to one of the end openings of the furnace, the other opening of which is exposed to the free air.

A substantial portion of the combustion air is therefore drawn through this ventilator and, in this manner, a considerable quantity of fresh air can pass through the furnace, for example, in the opposite direction to that of the displacement of the refuse, which makes it possible to provide a substantial quantity of oxygen as much for the combustion of the refuse as to activate post-combustion of the fumes by promoting also the interaction of this air drawn axially with the air blown radially through the grill, this generating interaction of various turbulent movements being capable of producing, through serious mixing of the fumes, their thor-.

ough mixing with the air and therefore favouring complete post-combustion.

This arrangement which improves post-combustion of the fumes contributes to the cooling and purifying of the gases prior to their evacuation into the atmosphere.

The quantity of air which is therefore conveyed in an axial direction is such that it preferably represents a substantial excess of air relative to the quantity necessary for stoechiometric combustion which is calculated for a statistically average composition of refuse.

In a preferred embodiment, the said double-walled drum made of thin sheet metal has the form of a truncated cone, the large base of which is connected to the opening for introducing matter to be incinerated and the small base of which constitutes an opening for evacuating ash, leading over the ash recepticle, the axis of said truncated cone which forms the axis of rotation of the furnace being inclined downwards in the direction passing from the opening for introducing matter to the opening for evacuating ash.

Therefore, when the drum rotates, the refuse can be gradually moved by the influence of gravity towards the opening for evacuating ash, which does not necessitate a complicated mechanism for the forward movement of the refuse.

The truncated shape selected for the drum has the advantage of being particularly functional and occupies only the minimum of space. In effect, towards the entrance where the refuse, which is only beginning to burn, occupies maximum space, the diameter of the drum is considerable whereas it is considerably reduced at the opposite end where the refuse, when totally burned and reduced to ash, only occupies a minimum space.

It can therefore be seen that the shape and inclined position of the drum make it possible to arrange a substantial space above the lower portion of the furnace, a space which can be used for the circulation of postcombustion gases.

In accordance with another important feature of the invention, the grill consists of movable elements which are assembled with the aid of temporary and losely' clamped fixing means.

In this manner, the entire grill or only certain components thereof can be conveniently replaced whenthis is found to be necessary, which does not necessitate putting the incinerator out of action for a prolonged time, to carry out total repair of the furnace.

It is possible to replace the grill with regular gaps in any desired manner, for example during normal operation for maintaining the vehicle, which hardly increases the time during which the incinerator is immobilised. In this respect the grill can be considered a consumable element of the incinerator, as is the combustible necessary for the burner.

In addition, owing to the particular fixing means in use, the different elements which form the grill can expand freely without producing deformation of the furnace.

In a preferred embodiment a mobile incinerator according to the invention is characterized in that the said means for introducing fresh air into the space between the girll and the lining of the furnace comprises a fixed annular cover or casing which is connected in a practically sealable manner to said space at one of the ends of the furnace, said space being closed at the other end and a blower being connected to said cover and provided with an inlet open to the free air.

It is also preferably provided that air deflectors directed towards the interior of the furnace are fixed on the said grill and positioned so as to divert the air from said blow orifices in a given direction. Said given direction is obviously that of the admission of air through a furnace, i.e. that of the admission of the quantity of air mentioned above, which is introduced through one of the end openings of the drum.

The function of these air deflectors is also to break up the refuse and prevent it from accumulating in a compact form against the grill of the rotary drum.

These deflectors also participate in the translational movement of the matter to be incinerated from the opening for the introduction of the latter into the furnace as far as the opening for evacuating ash, by assisting this matter to follow the rotational movement of the furnace.

In a preferred embodiment of the invention it is also provided that the said orifices are formed by punching the sheet metal which constitutes said grill inwards into the furnace, the axes of said orifices lying in the direc-' 7 tion of displacement of the matter to the interior of the vided with internal vanes forming racks for the reception of matter, a fixed neck located inside the wheel and provided with an upper inlet opening arranged below the upper portion of the wheel and a lower outlet leading into a passage which in turn leads to the opening for the introduction of matter into the furnace, and in that an alternately movable slide is slidably mounted in said passage and comprises a sealing wall for the outlet of the neck and an adjacent front wall for sealing said opening from the introduction of matter.

It can be understood that, when the slide is drawn back, the refuse can fall in front of its front wall, its other wall freeing the lower opening of the neck. During the forward movement of the slide, this refuse is introduced into the furnace whereas the lower opening of the neck is sealed. When the forward movement of the slide is terminated, its front wall seals the opening for the introduction of matter into the furnace.

This means for introduction of matter into the furnace has the important advantage of ensuring regular charging of the furnace, while permitting a certain amount of storage of material to be incinerated, in order to absorb irregularties in the collected refuse, particularly in the case where this matter is household refuse. In effect, the alternating movement of the slide ensures great loading regularity and, in the event of overloading, the refuse remains in the racks of the paddle wheel, owing to the fact that it cannot fall if the said neck is full.

The regularity of this loading is greatly responsible for ensuring perfect burning of the refuse in the furnace as well as ensuring optimum efficiency in operation.

It is also provided in accordance with the invention that the said burner is a burner with two heads, one of which is located approximately in the centre of the furnace, and the other close to the opening for evacuation of ash.

Therefore the burner head located approximately in the centre of the furnace drives, preheats and ignites the refuse while initiating post-combustion of the fumes which, when coming from the combustion zone of the refuse, meet this burner head on the outward journey out of the furnace.

The matter which has reached the lower part of the furnace and might be imperfectly burned is again subject to the action of the burner head located close to the opening for evacuation of ash, which practically eliminates the risk of unburned refuse falling into the ash recepticle.

The said means of post-combustion are preferably provided with an auxiliary burner, the feed control of which is connected to means for analysing the evacuated gases.

Therefore if the composition of the evacuated gases shows insufiicient burning of the fumes emanating from the furnace, the feed of the auxiliary burner is controlled and the burner ignited, which ensures a more complete combustion of the fumes.

A mobile incinerator according to the invention, in which the means of feeding the burner with combustible gas comprises a tank of liquified gas, an evaporator, and means of passing the evaporated gas to the burner, can also be characterized in that the evaporator comprises a bundle of tubes arranged at the bottom of the tank, one end of said bundle leading into a first collector connected to suction means, and the other end into a second collector which is connected to a two-way valve or shutter which is capable of bringing the collector into contact with a tubular exchanger subjected to the heat of the post-combustion gases. Therefore the heat emitted by the post-combustion of the fumes is partially recovered to ensure evaporation of the combustible liquid in the tank. This evaporation does not therefore necessitate additional expenditure of energy.

The said two-way shutter preferably comprises a control member capable of alternately controlling the connection between said second collector and the said tubular exchanger subjected to the heat of postcombustion gases, or between said second collector and an inlet for fresh air, said control member being subjected to the action of pressostat which receives the pressure of the evaporated combustible inside the tank.

It can be seen that this arrangement permits the pressure of the combustible gas in the tank to be regulated. In effect, if this pressure exceeds a predetermined value, the pressostat sends to the control member of the two-way shutter a signal so that the shutter permits the second collector to be fed with fresh air, which reduces evaporation and prevents the pressure from continuously rising. Therefore, great reliability is obtained in the use of the tank, and the risk of explosions is particularly eliminated.

0n the other hand, if the pressure of the combustible gas in the tank is too low, the pressostat sends via said control member such a signal that the shutter or valve establishes a connection between said second collector and the tubular exchanger subjected to the heat of post-combustion gases, which results in evaporation being accelerated.

It is also provided in accordance with the invention that the means of passing the evaporated gas to the burner comprises a low pressure circuit connecting the tank to the burner, and a high pressure circuit shunted onto the low pressure circuit, said high pressure circuit comprising an electrically operated shutter the control member of which is connected to the output of a thermostat which receives the temperature of the furnace as an input signal.

Therefore, if the temperature in the furnace is too low, the thermostat sends via the control member of the electrically operated shutter such a signal that the control member establishes a connection between the high pressure circuit and the burner, which obviously has the effect of increasing the temperature in the furnace.

On the other hand if the temperature inside the furnace is too high and there is a risk of the furnace being damaged, the thermostat sends via the control member of the electrically operated shutter such a signal that the shutter prevents connection between the high pressure circuit and the burner. The latter is therefore only fed by the low pressure circuit, which obviously results in a reduction in the temperature in the furnace.

By acting on the control of the thermostat, the ideal temperature for the operation of the furnace can therefore be determined in a particularly simple manner.

This control can be a function of the nature of the material to be burnt or of their state of dryness, or of other parameters.

A preferred embodiment of the invention is shown as an example in the accompanying drawings, in which:

FIG. 1 is a schematic representation in perspective of part of a mobile incinerator according to the present invention, showing the general arrangement of the furnace and means of introducing material to be incinerated;

FIG. 2 is a similar representation showing the means of post-combustion, cooling means, purifying means and means of evacuating combustion gases;

FIG. 3 is a schematic view and axial section showing the truncated drum forming the furnace as well as means of feeding said furnace with fresh air;

FIG. 4 is a view showing the structure of the rotary drum;

FIG. 5 is a section along the line V V shown in FIG. 4;

FIG. 6 is a section along the line VI VI shown in FIG. 4;

FIG. 7 is an axial section showing the configuration of the air deflectors as well as blow orifices of the grill;

FIG. 8 is a plan view corresponding to FIG. 7;

FIG. 9 is a schematic representation showing the configuration of the means for introducing matter to be incinerated into the furnace;

FIG. 10 is a schematic representation showing the evaporator of liquified gas as well as the device for regulating the pressure in the tank;

FIG. 1 1 is a schematic representation showing the device for regulating the temperature inside the furnace; and

FIG. 12 is a schematic representation showing the connection between the means of analysing postcombustion gases and the feed control of the auxiliary burner.

The mobile incinerator which is represented in FIGS. 1 and 2 and intended for the incineration of household refuse during the door-to-door collection of said refuse comprises a rotary furnace 1 fixed on the chassis or frame of a motor vehicle 2, said furnace being rotatably driven by a toothed wheel 3 which is in turn driven by a drive shaft 4. Below the furnace 1 there is arranged an ash recepticle 5 for collecting the ash from the front end of the furnace. The means of introducing matter to be incinerated into the furnace are arranged to the rear of the vehicle and schematically represented by reference numeral 6. These means, which will be described in more detail below, essentially comprise a paddle wheel 7, with a horizontal axis directed along the general axis of the vehicle, said wheel being drivable in any desired manner.

Between the furnace l and the cabin 8 of the vehicle, in the space schematically represented by the reference numeral 9, are arranged a tank 10 of liquid propane as well as the associated equipment for the furnace, comprising different control members, pressure and temperature control devices, pumps, auxiliary motors, etc. To the left of the ash receptical is arranged a water tank 1 1 for collecting the water for the purifying of combustion gases.

In the upper part of FIG. 2 are shown the means for permitting post-combustion of the fumes. These means comprise a post-combustion chamber arranged above the furnace and separated therefrom by a horizontal partition or wall 12. This chamber, which is connected to the rear charging opening of the furnace as shown by arrow 13, comprises vertical partitions or walls in the form of baffle plates or deflectors. The postcombustion chamber is also connected to gas cooling and purifying means shown in the lower part of FIG. 2 and arranged above the water tank 11. These means comprise a cooling chamber 16 connected to the postcombustion chamber, as shown by the arrow 17, the chamber 16 being divided into three compartments by two horizontal partitions, 118, 19 the lower compartment being connected to the water tank 11. The passage between the two lower compartments of the chamber 16, is shown by the arrow 20, located in the range of a spray head 21 which is fed with water from the water tank 11 via an inlet 22, a pump 23 and a pipe 24.

Finally the front part of the lower compartment of the cooling chamber is connected, as shown by an arrow 25, to the suction inlet 26 of a fan for evacuating fumes 27 and expelling into the atmosphere gases drawn into the inlet 26 in the direction of an arrow 28.

This same lower part of FIG. 2 also shows a blow fan 29 capable of sucking fresh air in from outside, through an inlet open to the free air, and of which the outlet 30 I is connected to an intake 31 for injecting air into the furnace, as well as a motor 32 for driving the shaft 4 via a conventional transmission.

As can be seen in FIG. 3, the rotary furnace 1 is produced in the form of a double-walled truncated drum, which is made of thin sheet metal and open at both ends at 33 and 34, and of which the axis 35, which is also its axis of rotation, is substantially inclined downwards in a line extending from the opening 33 for evacuating fumes to the opening 34 for evacuating ash.

The interior wall 36 of the drum forms a grill and is provided, for this purpose, with blow orifices 37. As

can be seen in FIGS. 7 and 8, these orifices are madev by punching the thin sheet metal forming the grill 36 inwards into the furnace, said punching operation being carried out in such a manner that the axis of these orifices 37 is directed towards the opening 34 of the drum.

Air deflectors 38, slightly inclined towards the opening 33, are also fixed inside the grill 36, and associated with each of the blow orifices 37 and formed by L- shaped angle irons the interior angle of which is directed towards the corresponding orifice 37.

The exterior wall of the furnace is sealed and forms a cover or casing 39. The structure of the rotary drum 1 is shown in FIGS. 4, and 6. This structure comprises essentially circular profiles 40 which are axially equidistant and the diameters decreasing from the opening 33 to the opening 34, said sections being connected by section forming side members or beams 41. The grill 36 is formed by movable, substantially rectangular, platelike elements 42 made of thin sheet metal and assembled with the aid of temporary and loosely clamped fixing means such as those shown in FIGS. 5 and 6. These fastening means comprise angle irons 43,44 mounted on axles 45, of which the ends are provided with stop pins 46 and which extend through the sections 40 and 41. Between the legs of these angle irons there is therefore arranged a gap 47 in which the edges of the elements 42 are accommodated.

It can be seen that this arrangement permits free expansion of the elements of the grill which are subjected to high temperatures, and this prevents the grill from being subjected to stresses capable of deforming it. On the other hand, it appears to be particularly simple to dismantle the angle irons 43 and 44, owing to the fact that it is sufficient, for this purpose, to extract the stop pins 46 from the ends of the axles 45. The used elements of the grill can therefore be easily replaced either partially or wholly in order to be replaced by new elements. Consequently this operation only necessitates a short-term immobilisation of the incinerator.

The means of introducing into the furnace a combustion gas, in this case fresh air, comprises a fixed annular cover or case 48 which is connected in a practically sealable manner to the space between the grill 36 and the cover 39 of the furnace at the front end of this space, the other end 49 of which is closed. Connected to the cover 48 is the intake 31 which is in turn connected to the outlet 30 of the fan 29 for sucking in fresh air, which has been discussed earlier.

The means of introducing fresh air into the furnace also comprises the fan 27 for evacuating fumes, which was also mentioned earlier. In effect, this fan sucks in fumes from outside the furnace, in the direction of the arrow 13 thereby causing a flow of fresh air through the opening 34 of the furnace, which is connected to the outer atmosphere as shown by an arrow 50 in FIG. 3.

The opening 33 for evacuating fumes is also connected to an opening 51 for introducing matter to be incinerated, which is capable of being sealed by an alternately movable slide, in a manner which will be described later.

A burner 52 with two heads 53 and 54 is arranged in the furnace l which has just been described. The burner 52 is arranged in such a manner that its flames strike the pile of refuse substantially along its longitudinal axis which, on account of the rotation, does not lie in the vertical plane passing through the lower generatrix of the drum. The interior pipe 55 of this burner, which is connected to a propane tank, also described below, and which feeds the two heads, is enclosed by a housing 56 which provides a small annular space around the pipe 55 and the heads. As this housing is open to the outer atmosphere, at 57, fresh air can be sucked therein and serves as a combustible gas for the propane gas flowing out of the burner heads, and as a cooling fluid for the heads and the interior pipe 55.

In accordance with the invention one of the heads 53 of the burner is located towards the centre of the furnace, whereas the other head 54 is in the vicinity of the opening 34 for evacuating ash;

Finally, FIG. 3 shows a schematic representation at 58 of a tubular heat exchanger submitted to the heat of post-combustion gases, said exchanger having a fresh air intake 59 and a hot air outlet 60. The function of this tubular exchanger will be also described later in the description.

The means 6 of introducing into the furnace matter to be incinerated, shown in FIG. 9, essentially comprises the rotating wheel 7 which is described earlier and is enclosed by a housing 711. This wheel is provided with interior vanes or paddles 61 which are evenly distributed and form racks for the reception of refuse. The wheel can be rotatably driven about its horizontal axis 62, by a hydraulic jack (not shown) which controls a ratchet driving device, a crown wheel being fixed to the circumference of the paddle wheel.

Inside the wheel there is arranged a slightly inclined neck 63 provided with an inlet 64 located below the rack of the upper generatrix of the wheel and with a lower outlet 65. This latter opening leads into a passage 66 which in turn leadsv tothe introduction opening 51 and in which there is slidably mounted a slide formed by a piston 67 capable of sealing the opening 51 and a metal sheet 68 which is welded to the upper part of the piston and can seal the opening 65. The piston 67 is integral with a control shaft 69 which is connected to the movable element of a hydraulic jack 70. When the piston 67 is drawn back, the closing sheet 68 can penetrate into a guide orifice 71 produced in a cover or hood 72.

In this Figure is shown the piston and its control members in solid outline for the advance position and by dot-and-dash lines for the retracted position.

The device for evaporating the liquid propane contained in the tank comprises a bundle of tubes 73 arranged at the bottom of the tank. One end of this bundle leads into a first collector 74 which is connected by a pipe 75 to a suction fan 76, and the other end of said bundle leads into a second collector 77. This collector 77 is connected by a pipe 78 to a two-way shutter or valve 79, of which the control member is formed by an electromagnet 80. One of the intakes of this shutter is connected to a fresh air inlet 81, whereas the other intake is connected to the hot air outlet 60 mentioned above.

The electromagnet 80 is connected to the outlet 82 of a pressostat 83 which is in turn connected to a probe or sampler 84 arranged in the upper part of the tank. (FIG. 10 shows a plan view of the bundle of tubes 73). Finally the evaporated propane can be evaporated from the tank through an outlet 85.

It should be noted that it would be possible to dispense with an additional suction fan such as the fan 76 by shunting the pipe 75 into the suction circuit of the blow fan 29.

The means of supplying the burner 52 with evaporated gas coming from the pipe 85 comprises a low pressure circuit 86 provided with a low pressure reducing valve 87 and a high pressure circuit 88 shunted onto the circuit 86 and comprising a high pressure reducing valve 89 and an electrically operated shutter 19 (FIG. 11). The coil 91 of the electrically operated shutter receives the output signal of a thermostat 92 connected to a temperature probe 93 arranged inside the furnace, in a representative zone of the functioning of the latter. This thermostat is also provided with a temperature input 94.

FIG. 12 shows a schematic representation of a postcombustion burner 95 arranged in the post-combustion chamber, preferably in a turning path followed by the fumes.

This burner is connected to the pipe 85 of the propane tank 10 by means of an electrically operated shutter 96 for controlling the feed.

Arranged in the gas evacuating pipe is a gas collector 97 connected by a pipe 98 to a gas analyser 99 located preferably in the space 9. At its output 100, this analyser provides an electric signal representative of the composition of the fumes, for example their percentage of carbon monoxide and the signal is amplified in an amplifyer I01 and delivered to the electrically operated control shutter 96.

The mobile incinerator just described operates as follows.

The refuse discharged into the rack which reaches the lower part of the paddle wheel 7 is drawn upwards into said wheel. When the rack in question is on a level with the upper part of the wheel, the refuse is discharged by the influence of gravity into the neck 63. At this moment if the piston 67 of the alternating slide is in a forward position a position in which it seals the opening 51 for introducing refuse into the furnace the metal sheet 68 seals the lower outlet 65 of the neck 63. During the return movement of the piston 67 to the rear, this refuse falls in front of the piston, the opening 55 being therefore cleared. Upon the following forward movement of the piston, this refuse is therefore forced fumes which come into contact with the head while passing out of the furnace and pass through its frame which, lying adjacent to the refuse and being directed by the axial depression, forms a screen over the entire free section of the furnace. Owing to the fact that the deflectors 38 are formed by angle irons which open towards the inlet 33, this refuse is subjected, during combustion to considerable comminution which favors oxygenation.

Part of the fresh air necessary for combustion is introduced into the furnace by means of the fan 29. The air is blown under pressure into the annular casing 48 from where it passes into the space between the grill 36 and the cover 39 of the drum. This air therefore vigorously cools the casing and the grill, before penetrating inside the furnace through the blow orifices 37, as shown by the arrows in FIG. 3. In this manner the refuse is subjected to transverse blowing which permits maximum oxygenation of the refuse by destroying compact blocks or moist agglomerates which might be formed in the furnace.

The other part of the fresh air necessary for combustion the most important part is sucked in through the opening 34 of the furnace, owing to the draft produced by the evacuating fan 27. The air passing through the furnace can therefore represent a considerable excess of air relative to the quantity necessary for stoichiometric combustion, and supplies a substantial quantity of oxygen as much for the combustion of refuse as for the activation of the post-combustion of fumes by also benefiting the action of this axially admitted air with the air blown radially through the grill, this generating interaction of various turbulant movements which produce thorough mixture of the fumes with the air through serious mixing of the fumes and therefore conditions them favourably for perfect postcombustion.

The fumes are sucked into the post-combustion chamber located above the furnace, and in which particularly the carbon monoxide can be completely burned and transformed into carbolic gas, then the gases are cooled in the cooling chamber 16, scrubbed during their passage in front of the spray head 21, and finally evacuated into the outer atmosphere in the direction of the arrow 28.

As indicated above, part of the heat emitted by the post-combustion of fumes is recovered by the tubular exchanger 58 (FIGS. 3 and 10).

Therefore, when the two-way shutter 79 establishes connectiom between the outlet and the connector 77, fresh air penetrates into the tubular exchanger 58,

Ill

is reheated there and moves into the bundle of tubes 73. Part of the liquid propane contained in the tank is evaporated and evacuated towards the burner through the outlet 85.

When the pressure in the tank reaches a predetermined value, this pressure is detected by the probe 84 and the pressostat 83 provides the electromagnet 80 with an electric signal in such a manner that the twoway shutter is commutated. The collector 77 is therefore connected to the fresh air intake 81, which has the effect of reducing evaporation of the propane. When the pressure has become sufficiently weak again, the shutter is once again commutated and hot air is again admitted into the bundle of tubes 73, which increases pressure again.

After passing through the bundle of tubes, the air is finally evacuated into the atmosphere through the pipes 75 and the fan or blower 76.

It can be seen that the method of evaporating the liquid propane according to the invention makes it possible to avoid any risk of explosion.

Moreover, the temperature inside the furnace can be kept practically constant. I

In effect, the burner 52 being for example fed by the high pressure circuit 88, if the temperature measured by the probe 93 exceeds the determining temperature of the thermostat 82, the latter sends to the coil 91 such an electric signal that the shutter 90 closes. The burner 52 is therefore only fed by the low pressure circuit 86 and the temperature of the furnace decreases. When the temperature becomes less than a determined value, the electrically operated shutter 90 opens and the burner is again fed under high pressure, which has the effect of increasing the temperature again.

The temperature of the furnace can be automatically operated in this manner and, by acting on the control of the thermostat, it is possible to note the condition and nature of the refuse, and particularly its rate of humidity. Therefore, total incineration of the refuse can be obtained irrespective of the type of refuse, in optimum operating conditions, by producing only minimum wear in the furnace and by consuming only the minimum of combustible.

In addition, it is possible to prevent toxic gases from being discharged into the atmosphere due to the auxiliary burner 95. In effect, if for example the portion of carbon monoxide in the fumes exceed a predetermined value, the electrically operated shutter 96 receives such a signal, which cause the shutter to open and the burner 95 to be brought into contact with the propane pipe 85. Therefore post-combustion of the fumes is accelerated, which makes it possible to eliminate the carbon monoxide.

What we claim is:

ll. In a mobile incinerator for collecting and incinerating refuse, said incinerator including a motor vehicle, a rotatable furnace mounted on the chassis of the motor vehicle, the furnace comprising a double-walled drum in the shape of the frustrum of a cone with the large base constituting an inlet opening for introducing material to be incinerated and the small base constituting an outlet opening for removing ash, means defining an ash collecting box positioned below the outlet opening, the axis of said frustrum of said cone comprising the axis of rotation of the furnace, said axis sloping downwardly in a direction from the inward opening toward the outlet opening, drive means for rotating the drum, means for introducing the material to be incinerated into the interior of the drum, burner means disposed in the drum, means for feeding inflammable gas to said burner means, and means for introducing the combustible gas, such as air, into the furnace by passing that gas through the inside wall of the drum, comprising the improvement wherein the inside wall of the drum comprises a gratelike structure constructed of thin perforated sheetlike metal, said gratelike structure having a plurality of openings formed therethrough, said gratelike structure also including air deflectors fixed thereto and directed inwardly toward the inside of the drum and positioned for deflecting the combustible gas which flows inwardly through said openings into the interior of said drum in a predetermined direction, the gratelike structure defining the inside wall coacting with the outside gas-tight wall of the drum to form an open annular space therebetween in which the combustible gas can freely circulate.

2. An incinerator according to claim 1, wherein said openings are formed in said gratelike structure by stamping a portion of said sheetlike metal inwardly toward the inside of said drum, the inwardly stamped portion of said sheetlike metal extending at least partially in the direction from the inlet opening toward the outlet opening so as to define the axes of said openings at least partially in the direction of movement of the material within the furnace.

3. An incinerator according to claim 2, wherein said air deflectors are disposed closely adjacent the downstream end of the inwardly stamped portions, said air deflectors extending at least partially in a direction toward the inlet opening of said drum.

4. An incinerator according to claim 1, wherein said gratelike structure comprises a plurality of substantially rectangular, perforated sheetlike grid elements.

5. An incinerator according to claim 4, further including means individually mounting each of said grid elements on said drum for permitting removal and replacement of said elements.

6. An incinerator according to claim 5, wherein said burner means comprises a continuously working burner having a plurality of heads spaced from one another along the length of the drum, said burner extending approximately from the middle of said furnace to a position adjacent the outlet opening, at least one of said heads being disposed closely adjacent said outlet opening.

7. An incinerator according to claim 1, wherein said burner means comprises a continuously working burner having a plurality of heads spaced from one another along the length of the drum, said burner extending approximately from the middle of said furnace to a position adjacent the outlet opening, at least one of said heads being disposed closely adjacent said outlet opening.

8. An incinerator according to claim 7, wherein said burner includes a second head disposed approximately midway between the inlet opening and the outlet opening. 7 

1. In a mobile incinerator for collecting and incinerating refuse, said incinerator including a motor vehicle, a rotatable furnace mounted on the chassis of the motor vehicle, the furnace comprising a double-walled drum in the shape of the frustrum of a cone with the large base constituting an inlet opening for introducing material to be incinerated and the small base constituting an outlet opening for removing ash, means defining an ash collecting box positioned below the outlet opening, the axis of said frustrum of said cone comprising the axis of rotation of the furnace, said axis sloping downwardly in a direction from the inward opening toward the outlet opening, drive means for rotating the drum, means for introducing the material to be incinerated into the interior of the drum, burner means disposed in the drum, means for feeding inflammable gas to said burner means, and means for introducing the combustible gas, such as air, into the furnace by passing that gas through the inside wall of the drum, comprising the improvement wherein the inside wall of the drum comprises a gratelike structure constructed of thin perforated sheetlike metal, said gratelike structure having a plurality of openings formed therethrough, said gratelike structure also including air deflectors fixed thereto and directed inwardly toward the inside of the drum and positioned for deflecting the combustible gas which flows inwardly through said openings into the interior of said drum in a predetermined direction, the gratelike structure defining the inside wall coacting with the outside gas-tight wall of the drum to form an open annular space therebetween in which the combustible gas can freely circulate.
 2. An incinerator according to claim 1, wherein said openings are formed in said gratelike structure by stamping a portion of said sheetlike metal inwardly toward the inside of said drum, the inwardly stamped portion of said sheetlike metal extending at least partially in the direction from the inlet opening toward the outlet opening so as to define the axes of said openings at least partially in the direction of movement of the material within the furnace.
 3. An incinerator according to cLaim 2, wherein said air deflectors are disposed closely adjacent the downstream end of the inwardly stamped portions, said air deflectors extending at least partially in a direction toward the inlet opening of said drum.
 4. An incinerator according to claim 1, wherein said gratelike structure comprises a plurality of substantially rectangular, perforated sheetlike grid elements.
 5. An incinerator according to claim 4, further including means individually mounting each of said grid elements on said drum for permitting removal and replacement of said elements.
 6. An incinerator according to claim 5, wherein said burner means comprises a continuously working burner having a plurality of heads spaced from one another along the length of the drum, said burner extending approximately from the middle of said furnace to a position adjacent the outlet opening, at least one of said heads being disposed closely adjacent said outlet opening.
 7. An incinerator according to claim 1, wherein said burner means comprises a continuously working burner having a plurality of heads spaced from one another along the length of the drum, said burner extending approximately from the middle of said furnace to a position adjacent the outlet opening, at least one of said heads being disposed closely adjacent said outlet opening.
 8. An incinerator according to claim 7, wherein said burner includes a second head disposed approximately midway between the inlet opening and the outlet opening. 